Method and Apparatus for Managing Session to Change a User Plane Function in a Wireless Communication System

1. A method performed by a session management function (SMF) in a communication system, the method comprising: determining whether to change a first user plane function (UPF) associated with a first protocol data unit (PDU) session of a terminal, the first PDU session being associated with a session and service continuity (SSC) mode 3; in case that the first UPF needs to be changed, transmitting, to an access and mobility management function (AMF), a first message including an identity (ID) of the first PDU session, a lifetime value for maintaining the first PDU session, and information indicating a PDU session establishment being required; and receiving, from the AMF, a second message for establishing a second PDU session of the terminal, based on the information, the second message including the ID of the first PDU session and an ID of the second PDU session, and wherein the second PDU session associated with a second UPF is established based on the ID of the second PDU session.

2. The method of claim 1 , wherein the first PDU session is released by the terminal before a timer associated with the lifetime value expires.

3. The method of claim 1 , further comprising: receiving, from the AMF, a third message for releasing the first PDU session before a timer associated with the lifetime value expires.

4. The method of claim 1 , wherein the ID of the second PDU session is generated by the terminal.

5. The method of claim 1 , wherein the first PDU session is released by the SMF in case that a timer associated with the lifetime value expires.

6. A method performed by an access and mobility management function (AMF) in a communication system, the method comprising: receiving, from a session management function (SMF), a first message including an identity (ID) of a first protocol data unit (PDU) session of a terminal, a lifetime value for maintaining the first PDU session associated with a first user plane function (UPF), and information indicating a PDU session establishment being required, the first PDU session being associated with a session and service continuity (SSC) mode 3; transmitting, to a terminal, the first message; receiving, from the terminal, a second message for establishing a second PDU session of the terminal, based on the first message, the second message including the ID of the first PDU session and an ID of the second PDU session; identifying the SMF based on the ID of the first PDU session included in the second message; and transmitting, to the identified SMF, a third message based on the second message, wherein the second PDU session associated with a second UPF is established based on the ID of the second PDU session.

7. The method of claim 6 , wherein the first PDU session is released by the terminal, before a timer associated with the lifetime value expires.

8. The method of claim 7 , wherein the first PDU session is released by the SMF, in case that a timer associated with the lifetime value expires.

9. The method of claim 6 , further comprising: receiving, from the terminal, a fourth message for releasing the first PDU session before a timer associated with the lifetime value expires.

10. The method of claim 6 , wherein the ID of the second PDU session is generated by the terminal.

11. A method performed by a terminal in a communication system, the method comprising: receiving, from an access and mobility management function (AMF), a first message including an identity (ID) of a first protocol data unit (PDU) session, a lifetime value for maintaining the first PDU session associated with a first user plane function (UPF), and information indicating a PDU session establishment being required, the first PDU session being associated with a session and service continuity (SSC) mode 3; determining to initiate a procedure to establish a second PDU session based on the information; and transmitting, to the AMF, a second message for establishing the second PDU session, the second message including the ID of the first PDU session and an ID of the second PDU session, wherein the second PDU session is established based on the ID of the second PDU session.

12. The method of claim 11 , wherein the first PDU session is released by the terminal before a timer associated with the lifetime value expires.

13. The method of claim 11 , further comprising: transmitting, to the AMF, a third message for releasing the first PDU session before a timer associated with the lifetime value expires.

14. The method of claim 13 , wherein the first PDU session is released by a session management function (SMF), in case that a timer associated with the lifetime value expires.

15. The method of claim 11 , further comprising: generating the ID of the second PDU session.

16. A session management function (SMF) in a communication system, the SMF comprising: a transceiver; and a controller configured to: determine whether to change a first user plane function (UPF) associated with a first protocol data unit (PDU) session of a terminal, the first PDU session being associated with a session and service continuity (SSC) mode 3, in case that the first UPF needs to be changed, transmit, to an access and mobility management function (AMF) via the transceiver, a first message including an identity (ID) of the first PDU session, a lifetime value for maintaining the first PDU session, and information indicating a PDU session establishment being required, and receive, from the AMF via the transceiver, a second message for establishing a second PDU session of the terminal, based on the information, the second message including the ID of the first PDU session and an ID of the second PDU session, wherein the second PDU session associated with a second UPF is established based on the ID of the second PDU session.

17. The SMF of claim 16 , wherein the first PDU session is released by the terminal before a timer associated with the lifetime value expires.

18. The SMF of claim 16 , wherein the controller is further configured to receive, from the AMF via the transceiver, a third message for releasing the first PDU session before a timer associated with the lifetime value expires.

19. The SMF of claim 16 , wherein the ID of the second PDU session is generated by the terminal.

20. The SMF of claim 16 , wherein the first PDU session is released by the SMF in case that a timer associated with the lifetime value expires.

21. An access and mobility management function (AMF) in a communication system, the AMF comprising: a transceiver; and a controller configured to: receive, from a session management function (SMF) via the transceiver, a first message including an identity (ID) of a first protocol data unit (PDU) session of a terminal, a lifetime value for maintaining the first PDU session associated with a first user plane function (UPF), and information indicating a PDU session establishment being required, the first PDU session being associated with a session and service continuity (SSC) mode 3, transmit, to a terminal via the transceiver, the first message, receive, from the terminal via the transceiver, a second message for establishing a second PDU session of the terminal, based on the first message, the second message including the ID of the first PDU session and an ID of the second PDU session, identify the SMF based on the ID of the first PDU session included in the second message, and transmit, to the identified SMF via the transceiver, a third message based on the second message, wherein the second PDU session associated with a second UPF is established based on the ID of the second PDU session.

22. The AMF of claim 21 , wherein the first PDU session is released by the terminal, before a timer associated with the lifetime value expires.

23. The AMF of claim 21 , wherein the controller is further configured to receive, from the terminal via the transceiver, a fourth message for releasing the first PDU session before a timer associated with the lifetime value expires.

24. The AMF of claim 21 , wherein the ID of the second PDU session is generated by the terminal.

25. The AMF of claim 21 , wherein the first PDU session is released by the SMF, in case that a timer associated with the lifetime value expires.

26. A terminal in a communication system, the terminal comprising: a transceiver; and a controller configured to: receive, from an access and mobility management function (AMF) via the transceiver, a first message including an identity (ID) of a first protocol data unit (PDU) session, a lifetime value for maintaining the first PDU session associated with a first user plane function (UPF), and information indicating a PDU session establishment being required, the first PDU session being associated with a session and service continuity (SSC) mode 3, determine to initiate a procedure to establish a second PDU session based on the information, and transmit, to the AMF via the transceiver, a second message for establishing the second PDU session, the second message including the ID of the first PDU session and an ID of the second PDU session, wherein the second PDU session is established based on the ID of the second PDU session.

27. The terminal of claim 26 , wherein the controller is further configured to release first PDU session, before a timer associated with the lifetime value expires.

28. The terminal of claim 26 , wherein the controller is further configured to transmit, to the AMF via the transceiver, a third message for releasing the first PDU session before a timer associated with the lifetime value expires.

29. The terminal of claim 26 , wherein the controller is further configured to generate the ID of the second PDU session.

30. The terminal of claim 26 , wherein the first PDU session is released by a session management function (SMF), in case that a timer associated with the lifetime value expires.